1. Field of the Invention
The present invention relates to a boundary device for mapping a resource reservation protocol intended to perform a communication quality control in an Internet Protocol (IP) network within a network configuration where an Asynchronous Transfer Mode (ATM) network exists between a sending terminal in one IP network and a receiving terminal in another IP network, and a method thereof.
2. Description of the Related Art
In recent years, the Internet being a communications network among computers has been making rapid progress with an increasing number of IP applications. Especially, the Internet has been advancing as a communications tool which is easier to use and realizes strong feelings of presence with the superposition of video and voice data and use of hyperlinks, which are realized by the WWW (World Wide Web).
Fundamentally, each node independently determines the route of an IP packet referred to as a datagram not by establishing a connection, but by making an end-to-end negotiation in an IP network. In a communications network performing such connectionless communications, data packets are normally routed and transferred for each hop (hop-to-hop transfer).
However, with the progress of the Internet, a network delay problem becomes more and more serious. One reason may be that a transfer means or a technique cannot catch up with an increase in network traffic. The principal cause, however, is the fact that the Internet is on the basis of a best-effort transfer.
Under a best-effort transfer environment where IP packets are transferred with the best effort, a repeater station at which packets arrive does not makes a distinction between the packets depending on users or applications, and only makes an effort to transfer the arrived packets to the next stage. Packets which cannot be transferred and overflow from a buffer are discarded.
Packet discarding is detected by a TCP (Transmission Control Protocol) higher than an IP layer at an end station, and is prevented by a retransmission procedure. However, there are problems in that packets not required for retransmission stay in a network, and that a transfer delay is not guaranteed for a real-time application.
To overcome such problems, a method for implementing the QOS (Quality Of Service) on the Internet was discussed in the IETF (Internet Engineering Task Force). A QOS control technique in an IP layer, which is based on the Version 1 of an RSVP (Resource Reservation Protocol), was standardized, and its implementation method has been studied up to now.
The RSVP is a control protocol for making a resource reservation in an IP layer, and performs the control shown in FIG. 1A. Under this control, control messages are exchanged between routers 2 supporting the RSVP in an IP network 1, an information sender (sending terminal) 3, and a receiver (receiving terminal) 4. With the exchange of the control messages, memory resources, etc. on a transmission line or within a router are reserved beforehand for an application of the sender 3, and its communication quality (QOS) is guaranteed. Normally, the sender 3 can provide the same information to a plurality of receivers 4 with a one-to-multiple communication. First of all, the sender 3 sends to the receiver 4 a Path message describing the traffic characteristic of information (contents) to be sent. The Path message is transferred along a transfer route (via routers), and distributed to each receiver 4.
The receiver 4 returns to the sender 3 a resource reservation message (Reserve message) describing a resource for which a reservation is required by referencing the contents described in the Path message. An intermediate router 2 merges reservation requests from a plurality of receivers 4, transfers the merged request to an upstream router 2 or the sender 3, and reserves transmission lines or memory resources for the plurality of receivers 4.
Next, the outline of a resource reservation mechanism using the RSVP is explained. The following explanation is based on the xe2x80x9cRSVP (Resource ReSerVation Protocol)xe2x80x94Version 1 Functional Specificationxe2x80x9d of the RFC (Request for Comments) 2205.
With the RSVP, a data flow for a particular destination and a transport layer protocol is defined as a session. A destination in a certain session is normally defined by xe2x80x9cDestAddressxe2x80x9d. This corresponds to an IP destination address of a data packet.
The procedure for making a resource reservation is composed of the following steps (1) through (4). Here, all of a sending terminal (sending side host), a receiving terminal (receiving side host), and nodes (routers) on a path are assumed to comprise the RSVP.
(1) Session establishment: a route between a sending and a receiving terminal is established by some routing protocol or other. Additionally, the receiving terminal joins a multicast group stipulated by the xe2x80x9cDestAddressxe2x80x9d according to an IGMP (Internet Group Multicast Protocol), etc.
(2) Path message transmission: a sending terminal periodically sends a Path message to a route established by a routing protocol (that is, to each DestAddress). The Path message describes the IP address of a sender, the information about the data such as a traffic characteristic, etc., which are sent by the sending terminal, and the IP address of a previous hop.
Each of the nodes on the path stores as a path state the information about the sending terminal and its session based on the information included in the Path message. Upon receipt of the Path message, each of the nodes updates its path state according to the contents of the Path message, and transfers the Path message to the next hop (node). Eventually, the Path message reaches all of receiving terminals.
(3) Resv message transmission: each of the receiving terminals sends a Resv message to the sending terminal. The Resv message is sent to a previous IP address (on an upstream side) stored in the path state of each of the nodes. This Resv message describes the QOS information requested by a receiving terminal, the information about a bandwidth reservation format, or the IP address of the destination node to which the Resv message is sent (that is, the previous IP address), etc.
(4) Process performed by each of the nodes receiving the Resv message: an RSVP controlling unit within each of the nodes, which has received the Resv message, makes a bandwidth reservation. The RSVP controlling unit stores reservation information as a reservation state based on the QOS information, the information about the bandwidth reservation format, etc. within the Resv message. Additionally, the RSVP controlling unit considers (merges) the reservation states obtained from respective routes, and finally stores the information for reserving a bandwidth as a traffic control state.
The RSVP controlling unit requests a traffic controlling unit within each of the nodes to reserve a bandwidth based on the information of the traffic control state. The traffic controlling unit comprises an admission controlling unit, which determines whether or not the requested QOS can be admitted. If this QOS can be admitted, a bandwidth is secured according to the contents of the reservation request. At this time, the Resv message is sent to the previous IP address stored in the path state of the corresponding node. If the QOS cannot be admitted, the Resv message is discarded and an error message is sent to the receiving terminal.
As a communications network having a form different from that of an IP network which performs such a communication quality control, an ATM network exists. The ATM is a transfer technique that is formed into specification by the ITU-T (International Telecommunication Union-Telecommunication Standardization Sector), etc. as a solution to a future broadband ISDN (Integrated Services Digital Network).
Originally, the ATM was intended to perform an efficient transfer and cost-effective network management regardless of media types by uniformly handling all services with short cells of fixed-length packets (of 53 bytes) and by transferring the cells. Thereafter, attempts are made to apply the ATM to an ATM LAN (Local Area Network), etc. by taking full advantage of its robust QOS control technique, and to apply to a service requiring high real-time performance, such as a video transfer, etc.
The ATM is on the basis of a connection-oriented communication, which is made after a virtual connection is pre-established with a VP (Virtual Path) or a VC (Virtual Channel) in a network composed of terminals and an ATM switch (exchange). The VP/VC is identified by a VPI (Virtual Path Identifier)/VCI (Virtual Channel Identifier), which is assigned to a header of an ATM cell. These identifiers are also referred to as ATM connection identifiers.
As a method for setting a VP/VC, a PVP/PVC (Permanent VP/Permanent VC), which is semi-permanently set by a management system (OPS), etc., and an SVP/SVC (Switched VP/Switched VC) set by a signaling procedure when an application demands exist. When a VP/VC is set, a user secures the VP/VC by declaring a bandwidth and a quality class, which are required for a communication.
With the procedure for establishing/releasing an SVP/SVC, a call is established/released by exchanging signaling messages stipulated by the ITU-T Q.2900 series.
FIG. 1B shows the procedure for establishing such a connection. In this figure, ATM switches (ATM SWs) 12 are arranged within an ATM network 11, and data are transferred between a sending terminal 13 and a receiving terminal 14.
When a call is established, a Setup message is sent from the sending terminal 13, and negotiations are made between the sending terminal 13, the ATM switches 12, and the receiving terminal 14. When a Connect message sent from the receiving terminal 14 reaches the sending terminal 13, a channel (connection) for user data is established.
Additionally, in the ATM, a message from one sender (Root) can be distributed by switches to a plurality of receivers (leaves) with a point-to-multipoint call establishing procedure as shown in FIG. 1C. In this case, setup messages (SETUP #1 and SETUP #2) are sent from a sender 15 to an initial receiver 18 via a switch 16, so that a call is established between the sender 15 and the receiver 18. Then, the next receiver 19 is added by an Add party message (ADD PARTY).
At this time, the switch 16 sends Setup messages (SETUP #3 and SETUP #4) to a receiver 19 via a switch 17 upon receipt of the message ADD PARTY from the sender 15. On receiving a Connect message (CONNECT) from the receiver 19, the switch 16 returns an Add party ack. message (ADD PARTY ACK.) to the sender 15. In this way, the receiver 19 is added as a party to the connection established between the sender 15 and the receiver 18.
Similarly, the sender 15 sends another Add party message, so that the third receiver 20 is added to the above described connection. Also fourth and subsequent receivers can be added with a similar procedure. Also the procedure for establishing a point-to-multipoint call, which is initiated by a receiver, is stipulated by the ATM Forum in addition to the above described procedure.
However, the following problems may arise when IP packets are transferred in the ATM by connecting the above described conventional IP and ATM networks.
An ATM transfer of IP packets itself is frequently made in a WAN (Wide Area Network), etc. In this case, a boundary device having both IP and ATM communications capabilities is arranged at a boundary between an IP and an ATM network. In this case, however, an IP packet transfer within the ATM network is a best-effort transfer using a connection of a point-to-point call (point-to-point connection), and a communication quality guarantee capability possessed by the ATM network is not effectively utilized.
With the advent of the RSVP being a signaling protocol within an IP network, it becomes possible to guarantee the quality within the IP network. However, a method for applying the RSVP to an ATM network has not been settled yet. Therefore, quality guarantee using the RSVP cannot be currently implemented between users within an IP network via an ATM network.
Additionally, to realize a QOS guarantee service on the Internet, an integrated service is currently being standardized by the IETF. Only proposal made as a signaling protocol for this service is the RSVP.
An object of the present invention is to provide a boundary device for mapping a communication quality control protocol such as an RSVP in an IP communication to an ATM communication, and a method thereof.
A boundary device according to the present invention comprises a receiving unit, a message processing unit, and a connection controlling unit. This device is intended to control a communication at a boundary between a first network that routes and transfers data packets in units of hops, and a second network that transfers data cells based on an established connection.
In a first aspect of the present invention, the message processing unit performs a communication quality control by processing control messages of a communication quality control protocol in the first network. The connection controlling unit establishes a control connection for transferring the control messages within the second network.
In a second aspect of the present invention, the receiving unit receives a resource reservation message of a communication quality control protocol in the first network via the second network. The message processing unit parses the resource reservation message. The connection controlling unit establishes a data transfer connection within the second network based on the information of the resource reservation message.
In a third aspect of the present invention, the receiving unit receives from a terminal within the first network a resource reservation message of a communication quality control protocol in the first network. The message processing unit parses the resource reservation message. The connection controlling unit establishes a data transfer connection within the second network based on the information of the resource reservation message.
Additionally, the present invention provides also a communication controlling method in a network including a first and a second network that route and transfer data packets in units of hops, and a third network that is arranged between the first and the second network and transfers data cells based on an established connection.
In a fourth aspect of the present invention, a control connection for transferring control messages of a communication quality control protocol in the first and the second network is established within the third network, and the control messages are transferred by using the established control connection between the first and the second network. Then, a data transfer connection is established within the third network based on the information of the control messages.
In a fifth aspect of the present invention, a resource reservation message of a communication quality control protocol within the first and the second network is transferred from the second to the first network via the third network. The resource reservation message is then parsed at the boundary between the first and the third network, and a data transfer connection is established within the third network based on the information of the resource reservation message.
In a sixth aspect of the present invention, a resource reservation message of a communication quality control protocol within the first and the second network is transferred from the second to the first network via the third network. The resource reservation message is then parsed at the boundary between the second and the third network, and a data transfer connection is established within the third network based on the information of the resource reservation message.